What is the HbA1c test for Diabetes?
Key Takeaways
Hemoglobin A1c, or HbA1c, is used to assess a person’s average blood sugar level over the past three months.
The test looks for an altered form of hemoglobin that’s created when blood sugar levels are high.
This test can be used to screen for diabetes, or to help guide treatment in those who have already been diagnosed with diabetes.
Certain other medical conditions can also cause a high HbA1c result, so it’s important to confirm the diagnosis of diabetes through another test.
There are various tests that can be useful to assess blood sugar control. One of these is a test known as the hemoglobin A1c test. This is often abbreviated as HbA1c, or simply A1c. This test is used to check a person’s average blood sugar level over the previous three months.
HbA1c testing can be used to screen for diabetes. For those who have already been diagnosed with diabetes, regular HbA1c testing is used to ensure that their treatment plan is working well to keep their blood sugar in a healthy range. This helps to reduce the risk of long-term complications such as kidney disease, heart disease, and vision loss.
How does the HbA1c test work?
The HbA1c test relies on checking for certain byproducts of high blood sugar levels. When blood sugar is high, the excess sugar begins binding to proteins in the bloodstream. This chemically changes those proteins.
Hemoglobin is a protein that’s used by red blood cells to transport oxygen in the bloodstream. When excess sugar binds to hemoglobin, it creates an altered form of hemoglobin known as hemoglobin A1c, or HbA1c. The HbA1c test measures the percentage of hemoglobin in the blood that consists of this altered form of hemoglobin.
Red blood cells are usually replaced about every three months, so the test gives an indication of what your blood sugar has been over that period of time. The more often your blood sugar has been high over the past three months, the more of your hemoglobin will be in the altered hemoglobin A1c form.
Although this is a useful test, it’s important to interpret the results carefully. For people with diabetes, HbA1c provides a good assessment of the risk of complications, such as vision loss and heart disease. However, studies have found that when HbA1c is used as a screening test, it may miss some cases of diabetes that would be caught by other methods of testing (such as a fasting glucose or oral glucose tolerance test). Conditions that alter how quickly your body makes new red blood cells, such as anemia or infections, can also affect your HbA1c. It’s important to consider the results of your HbA1c test in the context of your individual medical situation.
What do you need to do to prepare for the test?
You don’t need to do anything to prepare for the HbA1c test. Because the test measures your average blood sugar level over the past three months, it won’t be affected significantly by your most recent meal.
Only a very small amount of blood is needed for this test. It can be done on a drop of blood obtained by a finger prick. When the test is done this way, you’ll get your results within a few minutes. Although you may feel some discomfort when your finger is pricked, this is generally minor.
It’s also possible to do the HbA1c test on blood obtained from a blood draw. If you’re also having other blood tests at the same time, then it may make sense to get the blood for the test from the blood draw, rather than doing an additional finger prick. If the test is done in this way, then it will take a few business days to get your results back. There is sometimes minor bruising in the area after a blood draw, although putting pressure on the area helps to prevent this.
What do your HbA1c results mean?
When it’s used as a screening test, HbA1c can detect type 2 diabetes or prediabetes (an early form of type 2 diabetes). It’s generally not used to check for gestational diabetes or type 1 diabetes, because other tests are better for detecting these types. However, some studies have shown that HbA1c may be useful for detecting type 1 diabetes as well.
The results of a HbA1c test are reported as a percentage, which shows how much of your total hemoglobin is in the altered A1c form. If you take HbA1c as a screening test (meaning that you have not previously been diagnosed with diabetes or prediabetes), the results indicate:
Normal range: less than 5.7%
Prediabetes: 5.7% to 6.4%
Diabetes: greater than 6.5%
If you have symptoms that suggest that you could have diabetes, but your HbA1c test result is normal, it may be recommended that you take a fasting glucose or oral glucose tolerance test. The HbA1c test can sometimes miss cases of diabetes, which these tests may catch.
If you don’t have any symptoms of diabetes, and your HbA1c test shows a high result, it is recommended that you repeat the test at a later date or take another type of test to confirm that you really do have diabetes. Other factors can sometimes raise HbA1c, so it’s useful to confirm the result before concluding that you have diabetes.
If your HbA1c indicates prediabetes, making lifestyle changes can help to prevent this from progressing to full-blown diabetes. For those who have diabetes, a healthy lifestyle plan is also a cornerstone of treatment, and can make a huge difference in protecting your long-term health. Our NOVI Health team can support you in creating and maintaining a healthy lifestyle plan.
HbA1c results range for people with Diabetes
If you have already been diagnosed with diabetes, then HbA1c testing will also be used to evaluate how well your treatment plan is working. This allows your plan to be adjusted as needed to keep your blood sugar within a normal range as often as possible, which reduces the risk of long-term complications of diabetes (such as kidney disease and vision loss). The test is typically performed two to four times per year.
In general, for people with diabetes, the results of the test indicate that your blood sugar control is:
Optimal: less than 6.5%
Good: 6.5 to 7.0%
Acceptable: 7.1% to 8.0%
Suboptimal: greater than 8.0%
Your personal target may be somewhat different, and can vary based on your condition. Your treatment team will talk with you about what HbA1c target they recommend for you. If your test indicates that your blood sugar has been above the target, then you may need to switch diabetes medications, increase your medication dose, and/or make lifestyle changes to help better control your blood sugar.
Keeping HbA1c under 7% greatly reduces the risk of complications from diabetes, and those who achieve the optimal target of less than 6.5% have the lowest risk. Even if your HbA1c is higher than this, decreasing it can have a huge impact on your long-term health. One large study showed that, for every 1% reduction in HbA1c, the risk of:
Heart disease decreased by 14%
Food-related complications decreased by 43%
Vision loss decreased by 19%
Kidney disease decreased by 37%
Other types of blood sugar tests
There are also other types of tests that can be used to assess blood sugar. If your HbA1c result is high on a screening test, then one of these tests may be used to confirm the result and diagnose diabetes.
Blood glucose test. This checks the level of glucose, or sugar, in your blood.
A fasting blood glucose test is taken when you have not eaten for several hours (generally overnight). A level of 100 to 125 mg/dL (5.6 to 6.9 mmol/L) indicates prediabetes, while a higher level indicates diabetes. This test is often repeated on a different day to confirm the result.
People with diabetes may check their blood glucose levels one or more times per day in order to adjust their treatment.
Oral glucose tolerance test (OGTT). For this test, a fasting blood glucose level is taken. You then consume a drink with a measured amount of glucose, and blood glucose levels are checked again over the next few hours. This assesses how your body responds to glucose. At two hours, a glucose level of 140 to 199 mg/dL (7.8 to 11.1 mmol/L) indicates prediabetes, while a higher level indicates diabetes.
Possible causes of a high HbA1c result
In many cases, a high HbA1c result indicates that your average blood sugar has been high over the past three months. However, there are also other conditions that can cause HbA1c to be high. Some of these conditions include:
Anemia (such as that caused by iron or vitamin B12 deficiency)
Certain medications (such as opiates and aspirin)
Chronically high alcohol consumption
Chronic kidney disease
Genetic conditions that affect the structure of hemoglobin
Confirming a high HbA1c result with another test for diabetes, such as a fasting blood glucose or oral glucose tolerance test, helps to ensure that you truly have diabetes, rather than another condition that may raise HbA1c.
Where to go for the test and its cost
In Singapore, you may be eligible for a subsidized screening if you're aged 40 years or older. Eligible Singaporeans can receive an HbA1c test for just $5. You can check your eligibility here.
For those who are not eligible, most GP and specialist clinics offer this test for about $15 to $25.
Here at NOVI Health, we include the HbA1c test as a part of a complete health assessment. Our Assessment uses the HbA1c test to screen for diabetes, along with a variety of other tests designed to screen for common health problems that could otherwise go undetected. Many serious health issues don’t cause obvious symptoms in their early stages, so it’s important to receive screening even if you feel healthy.
If you have any symptoms that could indicate diabetes, such as increased thirst or frequent urination, it’s a good idea to seek a health assessment as soon as possible. Diagnosing diabetes early is important, because treatment can help to keep blood sugar under control and protect your long-term health.